ISIL militants lead away captured Iraqi soldiers dressed in plain clothes after taking over a base in Tikrit. / AP

by Jim Michaels, USA TODAY

by Jim Michaels, USA TODAY

WASHINGTON - The militants who seized Mosul, Tikrit and other key Iraqi cities are attempting to win over Sunnis in occupied areas by negotiating with tribal leaders, working with other Sunni groups and providing services.

The tactics are a marked contrast to their methods in 2004-06, when the militants were fighting U.S. forces in Iraq and often brutalized Sunnis who didn't directly support them.

"They are a learning organization; they're very adaptive," Bruce Riedel, a former CIA officer and an analyst with the Brookings Institution, said Monday.

If successful, the tactics may allow the insurgents to win over support from Sunnis and hang on to the territory they have gained in recent attacks. "That's very worrisome," said James Jeffrey, a former U.S. ambassador to Iraq.

The Islamic State of Iraq and the Levant (ISIL) traces its roots to al-Qaeda in Iraq, a Sunni insurgent group that focused on trying to drive American forces from Iraq. It later expanded operations into Syria and has since broken ties with al-Qaeda.

The group's earlier leader, Abu Musab al-Zarqawi, openly targeted other Sunnis who didn't support the group and regularly appeared in videos, maintaining a high profile. He was killed in 2006 by an American airstrike.

ISIL's current leader, who goes by the nom de guerre Abu Bakr al-Baghdadi, has kept a lower profile, which has probably helped him survive, analysts say. "We don't even know what his (real) name is," Riedel said.

Even though ISIL - also known as the Islamic State of Iraq and Syria, or ISIS - appears to be trying to win over Sunnis, it has shown no restraint when it comes to brutalizing Shiites. A longtime strategy of the group has been to trigger a civil war between Sunnis and Shiites.

Over the weekend, images on a militant website seemed to support claims by ISIL that they executed 1,700 Shiites from the Iraqi military who were captured in recent fighting.

In Iraq, Sunnis are a minority but have long dominated the nation's government and suppressed the majority Shiites and exiled many of their leaders. After the fall of Saddam Hussein, Shiites have dominated the government.

Sunnis have grown increasingly disgruntled, saying the government of Prime Minister Nouri al-Maliki has not supported them or included them in the government.

Some analysts said the militant group's radical ideology and brutality will eventually alienate secular Sunnis, even if they win some converts in the short term.

"It hasn't really changed its stripes," Riedel said of the jihadist group.

In Syria, when the group gains control of an area, ISIL quickly imposes its own strict form of Islamic law. Earlier this year, ISIL claimed it executed seven prisoners in an area it controlled in Syria, including two by crucifixion.

"Once they're in charge of an area, they impose their kind of rule," said Jeff White, a former Defense Intelligence Agency official and an analyst at the Washington Institute for Near East Policy.

Most of ISIL's financing comes from wealthy Sunni donors in Gulf Arab states, plus the group may have stolen millions of dollars from banks in Mosul since taking over that city, White said.